Security Matters is trading 17.38% higher at $2.22 after-hours; the cause of the rebound remains unconfirmed. - It closed at $1.89 on October 16, following a 47.50% regular-session drop. - Available listings showed no October 16 company headlines, and no verified company-specific announcement was identified. - The broad market was sharply lower, while Bitcoin and Ethereum moved modestly lower over 24 hours; neither clearly explains the rise. No after-hours volume or activity details were provided.